Transcription

1 University of Groningen Vasoregression in incipient diabetic retinopathy Pfister, Frederick IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2011 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Pfister, F. (2011). Vasoregression in incipient diabetic retinopathy: Angiopoietin-2 dependency and the effect of Erythropoietin and Carnosine treatment Groningen: s.n. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date:

4 Chapter 4 Introduction Diabetic retinopathy (DR) is a common microangiopathy in diabetes. Hyperglycemia, the central initiating factor in DR, induces pathological changes in the retinal vascular bed, even early when the retina is clinically unaffected. Pericytes with glial cells enveloping capillaries are important for the protection of endothelial cells against damages from the harmful environment within the retina. In DR, hyperglycemia results in loss of pericytes, followed by degeneration of endothelial cells and capillary occlusions [13, 24, 189]. Enge et al. [121] demonstrated the association of reduced pericyte coverage with retinopathy in a transgenic mouse model with conditional inactivation of the pericyte recruiting factor PDGF-B. They found that a 50% reduction of pericytes is the threshold for the development of vascular proliferation, indicating the crucial role of pericytes in the maintenance of vascular integrity and normal function. There is emerging evidence indicating that factors, such as the angiopoietin-tie2 system are involved in hyperglycemia-induced pericyte loss and the progression of DR. Angiopoietin-2 (Ang-2) is an important molecule involved in the adherence of pericytes to the capillaries ensuring the maturation, integrity and physiological functions of the vasculature [127, 162, 167]. Increasing evidence suggests that Ang-2 plays an important role both in physiological and in pathological angiogenesis, as well as in diabetic retinopathy [28, 135, 140, 162, 190]. Our previous data have demonstrated that Ang-2 is upregulated prior to morphological changes of retinal capillaries in diabetic retinopathy. Administration of Ang-2 into adult eyes results in pericyte loss. Reduction of Ang-2 in the Ang2LacZ murine retina protects capillaries from pericyte loss and decreases the numbers of acellular capillaries (ACs) in experimental diabetic retinopathy [28]. Moreover, we assessed pericyte coverage under overexpression of Ang-2 in the retinal development using a transgenic mouse line with overexpression of human Ang-2 under the mouse opsin promoter in the photoreceptor cells (mopsinhang2 mouse). We found reduced pericyte coverage and accelerated retinal vascular development in physiological and pathological angiogenesis in the retina demonstrating the effect of Ang-2 on capillary formation in the development [184]. However, the further fate of retinal capillaries in this gain-of-function model is unknown, Diabetes causes Ang-2 upregulation predominantly in the ganglion cell layer and inner nuclear cell layer in the retina [140]. Endothelial and glial upregulation of Ang-2 has been evidenced [ ]. By combining constitutive and hyperglycemia-inducible Ang-2 59

13 Retinal overexpression of angiopoietin-2 mimics diabetic retinopathy Discussion Our study demonstrates that constitutive overexpression of Ang-2 in the retinal photoreceptor cells induces vascular pathology, mimicking diabetic retinopathy. Furthermore, we show that constitutive overexpression of Ang-2 enhances further vascular damages in hyperglycemia. Retinal vasoregression is characteristic for DR. We observed that overexpression of Ang-2 in retinal neurons leads to pericyte loss and AC formation in the normoglycemic retina. The retinal vascular changes of normoglycemic mopsinhang2 mice resemble qualitatively and quantitatively those observed in 3 month diabetic wild type mice. Together with our previous data showing pericyte loss is linked to augmented Ang-2 from vitreous and glia [28], the data in present study reinforce the importance of Ang-2 in controlling pericyte coverage of mature retinal vessels and its crucial role in the development of DR. Compared with development of pericyte loss in diabetic wild type mice, hyperglycemia did not result in a further extent of pericyte loss in diabetic mopsinhang2 retinas at 3 months. The lack of progression in pericyte loss in diabetic mopsinhang2 retinas suggests that there might be a temporal validity of Ang-2 or a threshold for pericyte loss in mopsinhang2 retinas. Enge et al. [121] found a 50% reduction of PCs is the threshold for the development of proliferative DR correlated with PDGF-B. Similarly, we found that there likely is a threshold level of approximately 20% pericyte loss for Ang-2 dependent vasoregression. Nevertheless, this threshold was broken by long-term hyperglycemia of 6 months. In the combined model, hyperglycemia induces an additional release of Ang-2 from glial cells, explaining the further increase of pericyte loss and vasoregression in diabetic mopsinhang2 mice at 6 months. Other hyperglycemia-induced factors within the retina, which additively promote retinal vasoregression could participate in the further increase of retinal pericyte loss and AC formation in diabetic mopsinhang2 retinas. In the normal retina, Ang-2 is expressed in neuronal cells and in some undefined cell types of the ganglion cell layer [135]. In the diabetic retina, endothelial cells and glial cells might be the main sources of Ang-2 [ ]. An increase of Ang-2 expression has been described in the inner nuclear layer after 6 months of hyperglycemia [140]. However, the precise mechanisms underlying Ang-2 upregulation in the diabetic retina remain to be elucidated. Recently, Yao et al. [193] reported that hyperglycemia induces intracellular formation of methylglyoxal which activates Ang-2 transcription through modification of msin3a. In a parallel experiment using the same mopsinhang2 mice, we showed that 68

14 Chapter 4 overexpression of Ang-2 results in elevated pericyte migration in certain pericyte subpopulations, indicating a novel mechanism for pericyte loss in DR [194]. In the present study, we quantitatively demonstrate that overexpression of Ang-2 results in significant pericyte loss and formation of ACs comparable to diabetic wild type mice. Thus, mopsinhang2 mouse presents a suitable mouse model for elucidating mechanisms involved in retinal vasoregression related to elevated Ang-2 levels. In the present study, we did not observe an increase in RNA expression of Ang-2 in diabetic wild type mice in contrast to what we reported before in the rat [28]. Species difference may be one explanation, and the other could be the early time point studied (3 weeks), as vascular damage in the mouse retina is generally milder than in the rat. In comparison with our previous observation, a 20% decrease of pericyte coverage in diabetic mouse retina at 6 months has been revealed in diabetic rat retina at 3 months after diabetes induction [28]. In this study, we provide evidence that human Ang-2 is highly expressed in transgenic retinas, resulting in earlier vascular pathology in the retina. In conclusion, our study provides evidence that Ang-2 plays a critical role in retinal vascular maintenance and in retinal vascular damage of early diabetic retinopathy. These data contribute to the understanding of Ang-2 function in retinal vasoregression and thus are important for development of therapeutic interventions to prevent diabetic retinopathy. 69

15 Retinal overexpression of angiopoietin-2 mimics diabetic retinopathy Acknowledgements This study was supported by grants from the DFG, the DDG and the GRK 880. The authors thank Petra Bugert, Nadine Dietrich and Valerie Schwarz for their grateful support. 70

University of Groningen Control of metabolic flux by nutrient sensors Oosterveer, Maaike IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it.

Supplementary Figure 1 MicroRNA expression in human synovial fibroblasts from different locations. MicroRNA, which were identified by RNAseq as most differentially expressed between human synovial fibroblasts

University of Groningen Vasoregression in incipient diabetic retinopathy Pfister, Frederick IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from

Supplementary Figure S1 Phylogenetic analysis of human and chicken importins. Only five of six importins were studied because importin-α6 was shown to be testis-specific. Human and chicken importin protein

Electronic Supplementary Material (ESI) for Chemical Science. This journal is The Royal Society of Chemistry 2017 A smart ZnO@polydopamine-nucleic acid nanosystem for ultrasensitive live cell mrna imaging

Bioinformatics in Medical Product Development SMPD 287 Three Beta Thalassemia Sami Khuri Department of Computer Science San José State University Hemoglobin Outline Anatomy of a gene Hemoglobinopathies

PATIENTS AND METHODS Subjects Twenty-nine morbidly obese subjects involved in a gastric surgery program were enrolled in the study between October 25 and March 21. Bariatric surgery was performed in patients

University of Groningen On the relevance of carnosine and carnosinase for the development of diabetic nephropathy Riedl, Eva Maria Susanne IMPORTANT NOTE: You are advised to consult the publisher's version

Integration Solutions (1) a) With no active glycosyltransferase of either type, an ii individual would not be able to add any sugars to the O form of the lipopolysaccharide. Thus, the only lipopolysaccharide

Development of RT-qPCR-based molecular diagnostic assays for therapeutic target selection of breast cancer patients Sangjung Park The Graduate School Yonsei University Department of Biomedical Laboratory

Supplementary data: Supplementary Material and Methods Animal preparation The animals were housed in standard cages with ad libitum access to both food and water. During the imaging sessions, the animals

Bacterial Gene Finding CMSC 423 Finding Signals in DNA We just have a long string of A, C, G, Ts. How can we find the signals encoded in it? Suppose you encountered a language you didn t know. How would

University of Groningen The RET gene and its associated diseases Hofstra, Robert Martinus Wouter IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite